Roentgen tube control



K. BISCHOFF ROENTGEN TUBE CONTROL Feb. 14, 1939.

Filed March 26, 1936 Patented Feb. 14, 1939 ROENTGEN TUBE CONTROL KurtBischoff, near Erlangen, Germany, assignor to the firmSiemens-Reiniger-Werke Aktiengesellschaft, Berlin, Germany ApplicationMarch 26,

1936, Serial No. 71,063

In Germany March 29, 1935 9 Claims.

The present invention relates, broadly speaking, to the art ofcontrolling high tension apparatus and is particularly concerned with anew method and with novel and improved means for controlling Roentgentubes in such a manner as to protect them against overloads.

It will be advisable to refer briefly to the prior art in order tofurnish a basis for a better understanding of the detailed descriptionof my invention which is. yet to follow. However, in the course of thefollowing discussion, I will describe in detail only those parts andtheir functions which are new; what may be considered old and known inthe art will be explained only to such 5 extent as is necessary forsupporting the understanding of my invention.

In prior arrangements for protecting Roentgen tubes against overloads,the control means for the operating factors such as tube tension orvoltage e, tube current i, and load-time t-(or the control means for theresulting or derived factors such as work input and milliampere/secondproduct) are coupled with one another and are actuated in such a mannerthat the tube is always operated with the maximum permissible load. Thedisadvantage of such an arrangement resides in the fact that the tube isoperated up to its load limit even in cases where the full utilizationof its maximum load capacity is not required, and accordingly, theuseful life of the tube is thereby greatly shortened. In another knownarrangement of this class, the control means for the previouslymentioned operating factors are not coupled with one another but withthe adjustable maximum current or cut-out switch, in such a manner, thatthe switch releases or disconnects when that load I limit is exceededwhich is permissible for the Roentgen tube in use. In this latter case,we are faced with the disadvantage that a Roentgen exposure might'faildue to wrong setting or adjustment of the control means and consequentpremature release of the cut-out switch provided for protecting thetube.

These disadvantages may be avoided and Roentgen tubes may be protectedto some extent,

after determining the individually adjustable load range'which isdependent on the third factor, thus preventing an overload adjustment orcontrol prior to subjecting the tube to the load, and indicating suchoverload adjustment by means of a device adapted to show simultaneouslyall three load determining factors or values derived therefrom. Theindicating device may be so constructed as to show the margin betweenthe adjusted load value and the load capacity or load. limit of thetube.

The above intimated prior development is based on the fact that the loadof a Roentgen tube is determined by the three variables mentionedpreviously, namely, the tube tension or voltage 6 (kV), the tube current1 (mA), and the load time 25 (sec). The limit loads which arepermissible for any given Roentgen tube may be represented in acoordinate system in the form of curves, wherein two of the threevariables are used as coordinates, while the third value serves as aparameter. For example, the limit loads which are admissible in aRoentgen tube may be expressed in a curve system wherein t=const., thatis, a coordinate system with the coordinates (2 (kV) and 2' (mA),wherein the individual curves correspond to different constant values oft. It is similarly possible to express the limit loads in a system withthe coordinatesi (mA) and 15 (sec), wherein e=const. The values 2' and tare preferably plotted in such a coordinate system on a logarithmicscale because in that case the curves e=const. will assume an almostlinear form.

As previously suggested, such a load diagram may be employed inconnection with the control board of the Roentgen equipment, andpointers or fingers may be provided for indicating upon the respectivediagram axes the values of the corresponding operating factors. Thepointers may also be suitably coupled with the respective control meansin such a manner that they indicate the operating values adjusted or setby these. Such an arrangement furnishes a certain safeguard againstoverloads, inasmuch as it affords an indication of the various valuesand factors involved in the operation of Roentgen tubes.

My present invention represents an improvement over the priordevelopments mentioned above and avoids the drawbacks and disadvantagesnoted previously in connection with the customary control arrangementsfor and mode of operation of Roentgen tubes. It is understood, ofcourse, that the instant invention is explained and described herein inconjunction with Roentgen apparatus chiefly for the-purpose of guidingothers in applying the novel features in practice, but not to indicateany limitations outside of those that are imposed by the prior art. Someof the salient objects are noted below.

A specific object of the present invention, in an arrangement of theclass generally defined above and including the device for preventingand indicating an overload adjustment or overload condition, resides inthe provision of a movable member, e, g., a pointer or finger, theadjusted operative position of which corresponds at any time to. thework input of the tube, and means for cooperative actuation of suchmovable member with a timing switch, in such a manner that the maximumpermissible load time corresponding to any given work input or themaximum permissible work input corresponding to a given load time areindicated, whereby the over-stepping of this load value or load limit isprevented.

Another object is realized in the provision of means for mechanically orelectrically coupling the above noted movable member with thetubecurrent or heating-current control means and with the means forcontrolling the tube voltage.

A further object receives expression in an arrangement wherein thetube-current or heatingcurrent control means and the control provisionsfor the tube tension each govern an auxiliary circuit in such a mannerthat the currents flowing in these circuits are proportional to theadjusted values of the tube current and tube tension and are fed to themovable member which is constructed in the form of a wattmeter system.

Still another object refers to the provision of means for governing oradjusting the current in the corresponding previously noted auxiliarycircuits and mechanically or electrically coupling said means with thetube-current or filament heating-current control and with the controlfor the tube tension.

A further object of the invention is concerned with an arrangement aspreviously intimated, wherein the adjustment of the movable member andof the timing means are directly indicated on, and readable from, acommon dial or scale.

Another object has to do with the provision of means whereby an overloadadjustment of the tube is prevented by a movable stop member which ismechanically or electrically coupled with the previously noted movablemeans or pointer, and controls or limits the adjustment or setting ofthe timing switch.

Still another object is realized by the provision of means whereby anoverload adjustment of the tube is prevented by a movable stop memberwhich is mechanically or electrically coupled with the timing means andcontrols or limits the adjustment or setting of the previously intimatedmovable member or pointer.

Other objects and features will appear from the following detaileddescription which is rendered with reference to the drawing. In thedrawing:

Figure 1 illustrates a circuit diagram of a new system embodying thefeatures of my invention, and specifically a system wherein the controlmeans for the operating values of the tube are coordinated with thetiming device; and

Figure 2 represents a modification of my new system wherein auxiliarycircuits are employed for control and indication together with acoordinate control of the timing device.

It will be recalled from the foregoing discussion that the load capacityof a Roentgen tube may be characterized accurately by a single curvewhichindicates theload capacity at a given voltage 6 as a function ofthe current i and as a function of the load time t. On this fact is alsobased the use of a movable member, for example, a pointer for preventingor indicating an overload adjustment, the setting of the pointercorresponding at any time to the input in kilowatts which is supplied tothe tube at such setting, and the movable member cooperating with a timeswitch in such a manner that the maximum permissible load time at agiven input or the maximum permissible input at a given load time can berecognized and the overstepping of this load value made impossible.

The present invention will now be described in detail with reference tothe Figures 1 and 2 which show schematic circuit diagrams and therelated control and indicating devices.

Referring now particularly to Figure 1, the

Roentgen tube I I is supplied with current from g the high tensiontransformer I2 and the filament or heating current transformer I3. Thesetransformers are connected to the commercial current supply I4. Theconnection and disconnection of the high tension transformer I2 takesplace by means of a protecting switch I5 which is controlled by thetiming device I6. The Roentgen voltage or tension is controlled in theusual manner by means of the control device I! and the tube current andfilament current, respectively, by means of the control device It insuch a manner that the tube tension and the tube current will changeproportionally with the adjustment or setting of the control devices I1and I8. The function of these control devices will be readilyunderstood, as the device I! is a potentiometer, while the device I8 isa variable resistance.

The control knobs or handles I1 and I8 for operating the control devicesI! and I8 actuate the multiplication gears I9, causing a multiplicationof the values of the tube current i and the tube tension e and actuatinga pointer 22 by means of the roller 20 and the rack 2|. The setting ofthe pointer 22, therefore, corresponds to or indicates the power inputwhich is supplied to the tube. The multiplication gear will be presentlydescribed more in detail. Upon the rack 2I is secured an intermediatemember 23 which may be exchanged when a Roentgen tube is used which hasa different load degree or capacity.

The pointer or indicator 22 and the adjusting or setting pointer 24 ofthe timing switch I6 operate over a common scale in such a manner thatit can be directly read from the scale whether the tube is overloaded atthe adjusted values, namely,

at the determined tube input indicated by the pointer 22 and at thedetermined load time t indicated by the pointer 24. Overloading may beprevented, if desired, by equipping the pointer 22 or the finger 24, orboth, with stops 41, thereby limiting the adjustment of the input or theload time.

The multiplication gear arrangement I9 is shown only in sufficientdetail so that its operation may be understood. When the tube current isto be adjusted, the handle I8 on shaft 40 is depressed against thetension of spring 45 and is rotated until the pin 46 enters a slot inthe head of the tubular shaft 4!. At the same time the gear 42 on thelower end of shaft 40 meshes with gear 43. Rotation of the handle I8will now rotate the shaft 4| to raise or lower the control device I8,depending on the direction of rotation, and will also rotate shaft 44 bymeans of gears 42 and 43. The adjustment of the tube tension is carriedout in a similar manner by means of handle ll', depression and rotationof which raises or lowers the control device I! and simultaneouslyrotates the shaft 44. The arrangement is such that the eifects of thecurrent and tension adjustment on" shaft 44 are cumulative. That is, anadjustment to increase the current, and also an adjustment to increasethe tension, should rotate the shaft 44 in the same direction, and thisdirection, moreover, should be such as to advance the roller 20 to theleft.

In the embodiment shown in Fig. the Roentgen tube ll, transformers I2and I3, and switch I 5 are the same as the correspondingly numberedparts in Fig. 1, but the multiplication gear is replaced by anelectrical arrangement. Two handles may be employed, similar to I1 and[8 of Fig. 1, and hence not shown in the drawing. These handles may bemounted on threaded shafts and are used to raise and lower the controldevices 26 and 21, respectively. The control devices 26' and 21' notonly cooperate with the resistances 28 and 29 to regulate the tubetension and current, but also cooperate with the resistances 2'6 and 21which are included in auxiliary circuits. The arrangement is such, ascan be seen from the drawing, that an adjustment of control device 26,for example, which is effective to increase the tube tension, is alsoeffective to increase the current in the corresponding auxiliarycircuit. That is, the currents in the auxiliary circuits, respectively,are proportioned to the tube tension and tube current. The auxiliarycircuits include the windings of a meter 3|], the indicator or needle 3|of which shows upon the scale 32 a value corresponding to the inputsupplied to the Roentgen tube. The predetermined load time t, which isadjusted or set by means of the timing device 34, will also be indicatedon the scale 32 by means of the pointer 33, the latter beingmechanically coupled with the time switch 34 by means of theexchangeable intermediate control member 35 and a flexible band, asshown. The control member 35 may be constructed in the form of a cam soshaped as to produce a non-linear movement of the pointer 33 withrespect to the setting of the timing device.

The embodiment shown in Fig. 2 has an advantage over the one shown inFig. 1, in that the indicator or pointer 3| (unlike the pointer 22 inFig. 1) indicates the input supplied to the tube with substantialaccuracy, even though the voltage of the commercial current source mayfluctuate. This is true because the voltage fluctuations not only affectthe tube tension and current, but also affect the current in theauxiliary circuits.

Changes will suggest themselves to those experienced in the art, and maybe made as far as detail parts or the structure thereof or placement inthe total arrangement are concerned if conditions make it desirable ornecessary. Certain structures have been shown and described and othersthat may take their place have been indicated sufficiently to enablethose who are versed in the art to carry out the invention in all itsfeatures and embodiments. Details which I have not specificallydescribed are of such a character that they will be readily understoodby those to whom the invention is addressed. It is understood,therefore, that any structure or mode of operation or both will beconsidered as my invention if carried out within the scope and spirit ofthe following claims, wherein I have defined what I believe is myinvention and what I desire to have protected by Letters Patent.

I claim as my invention:

1. The combination, with a Roentgen tube, of means for adjusting thevoltage applied between the anode and cathode, means for independentlyadjusting the current flow between the cathode and the anode, and apower indicator jointly controlled by said adjusting means.

2'. The combination, with a Roentgen tube, of means for adjusting thevoltage applied between the anode and cathode, means for independentlyadjusting the current flow between the cathode and the anode, anindicator, and means whereby the voltage adjusting means and currentadjusting means jointly control said indicator to show a valuecorresponding to the product of the adjusted voltage and current.

3. The combination, with a Roentgen tube, of means for adjusting thevoltage applied between the anode and cathode, means for adjusting thecurrent flow between the cathode and the anode, an indicator, mechanismwhereby the said adjusting means jointly control said indicator, and acam included in said .mechanism whose curvature depends on thecharacteristics of the tube, the said cam serving to determine the ratioof indicator change to voltage and current change.

4. The combination, with a Roentgen tube, of movable means for adjustingthe voltage applied between the anode and cathode, movable means foradjusting the current flow between the cathode and the anode, anindicator, apparatus whereby the said adjusting means jointly move saidindicator, and means for introducing a predetermined variation in therate at which the indicator movement follows the movement of saidadjusting means.

5. The combination, with a Roentgen tube, of means for adjusting thevoltage applied between the anode and cathode of the tube, means foradjusting the current flow between the cathode and the anode, a timeswitch for stopping the operation of the tube after a predeterminedtime, a pointer and scale for indicating the setting of said timeswitch, a second pointer cooperating with said scale, and means wherebythe said adjusting means jointly control said second pointer.

6. The combination, with a Roentgen tube, of means for adjusting thevoltage applied between the anode and cathode of the tube, means foradjusting the current flow between the cathode and the anode, a timeswitch for stopping the operation of the tube'after a predeterminedtime, and means including a common scale for indicating the setting ofsaid switch and the power input to the tube as determined by theadjusted values of voltage and current.

7. The combination, with a Roentgen tube, of circuits for supplyingpower to said tube, means for adjusting the voltage applied between theanode and cathode of the tube, means for adjusting the current flowbetween the cathode and the anode, two circuits separate from and inaddition to said power circuits, means for causing current flow in saidadditional circuits, respectively, proportional to the tube voltage andcurrent, and a meter common to said additional circuits.

8. The combination, with a Roentgen tube, of circuits for supplyingpower to said tube, means for adjusting the voltage applied between theanode and cathode of the tube, means for adjusting the current flowbetween the cathode and the anode, two circuits separate from and thevoltage applied to the cathode anode circuit, means for adjusting thecathode heating current to vary the cathode anode current independent ofthe voltage, a time switch for predetermining the load time, and meansfor directly comparing the setting of said switch with the power inputto said tube as determined by the adjusted value of anode voltage andcathode heating current.

KURT BISCHOFF.

